sustainability

Article

Analysis of CO2 Emission Characteristics of ConcreteUsed at Construction SitesTae Hyoung Kim 1,*, Chang U Chae 1, Gil Hwan Kim 2 and Hyoung Jae Jang 3

1 Building and Urban Research Institute, Korea Institute of Civil Engineering and Building Technology,Daehwa-dong 283, Goyandae-Ro, ILsanseo-Gu, Goyang-Si, Gyeonggi-Do 10223, Korea; cuchae@kict.re.kr

2 Building Project Operation Division, GS Engineering & Construction, Gran Seoul 33, Jongro, Jongro-Gu,Seoul 03159, Korea; khkim6@gsconst.co.kr

3 Technological Development Team, Hanyang Corporation, 558 Songpadae-Ro, Songpa-gu, Seoul 05510,Korea; duethj@ hycorp.co.kr

* Correspondence: kimtaehyoung@kict.re.kr; Tel.: +82-31-9950-838; Fax: +82-31-9100-361

Academic Editor: Muge Mukaddes DarwishReceived: 5 February 2016; Accepted: 5 April 2016; Published: 8 April 2016

Abstract: As the greenhouse gas reduction goal of 37% below business-as-usual (BAU) by 2030, theconstruction industry is recognized as an anti-environment industry for mass consumption/masswaste; thus, members of the industry are requested to make efforts to transform it into anenvironment-friendly industry. Concrete, a common construction material, is known to emitlarge amounts of environmentally hazardous waste during the processes related to its production,construction, maintenance, and demolition. The amount of greenhouse gas (GHG) emissions bythe product is specified in a ready-mixed concrete report whenever concrete is sold commercially.Hence, there have been many studies addressing the quantitative evaluation and reduction of theenvironmental effects of concrete. This study aims to introduce a method for assessing the amountof carbon dioxide emission from the processes of producing concrete. Moreover, we measuredthe quantities of CO2 emission of about 10 under-construction projects, including office buildings,apartment buildings, and high-rise residential buildings in South Korea. Using the assessmentresult, we analyzed the CO2 reduction performance of an office building in South Korea and drewconclusions about measures for reducing CO2 emission.

Keywords: concrete; life cycle assessment (LCA); CO2 emission characteristic; construction site

1. Introduction

The amount of energy consumption and CO2 emission from the Korean construction industryaccounts for 23% of the total industry energy consumption and 40% of the total CO2 emission. As thegreenhouse gas reduction goal of 37% below business-as-usual (BAU) by 2030, the constructionindustry is recognized as an anti-environment industry for mass consumption/mass waste; thus, itis necessary to make efforts to turn it to an environment-friendly industry [1]. Considering that CO2

emission per capita in Korea increased by 113% from 1990, which represents the largest increase in CO2

emission among OECD countries, Korea also needs detailed environmental policies for CO2 reduction.Because concrete, which is the main material used in the construction industry, emits a large amount ofCO2 during the production of raw materials such as cement, aggregate, etc., research on CO2 emissionemitted from concrete production is direly needed.

The seven major building materials accounting for more than 90% of building greenhouse gas(GHG) emissions include concrete, a reinforcing rod, and section steel. Among the CO2 emissionsgenerated by these major building materials, concrete accounts for 70% [2].

The types of concrete (mix design, strength) used varies according to building structure, buildingtype and region. In the Republic of Korea, in particular, the concrete mix design significantly differs

Sustainability 2016, 8, 348; doi:10.3390/su8040348 www.mdpi.com/journal/sustainability

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depending on whether the concrete is used inland or in a coastal area for prevention of chloride-inducedcorrosion. Therefore, an assessment of CO2 emission and an analysis of their characteristics againstthe concrete used in diverse construction sites is needed.

Therefore, the assessment of CO2 emission is very important for achieving the national-level CO2

reduction objective.Recently, efforts to reduce CO2 emission are being made through the use of procurement systems

for low-CO2-emission materials and the application of high-strength concrete at construction sites.As a part of such research, there is a demand for the establishment of a quantitative assessment methodof CO2 emission from concrete production to site procurement and a proposal of a CO2 reduction planat construction sites using this [3].

This study attempts an assessment of CO2 emission against concrete among the major buildingmaterials and analyzes the characteristics on which building types (apartment, office) and regions(Seoul, Incheon, Ulsan) are dependent.

In addition, a CO2 emission reduction plan is proposed based on the result of the assessment ofCO2 emission.

The concrete production was divided into the following stages: raw material, transportation,and manufacturing.

The input materials, transportation distance, and energy usage data of each stage were used forassessing CO2 emission.

The CO2 emission levels calculated as such were divided and based on material characteristics,building type, and local characteristics.

2. Literature Review

Kim et al. [4] analyzed the CO2 emission reduction rate of long-life buildings using highdurability and maintenance technologies for standard buildings. The CO2 emission of thebuildings was evaluated by dividing into construction, operation, maintenance/management, anddismantlement/disposal stage. Roh et al. [5] developed an embodied GHG assessment system forbuilding materials in the Korea Green Building Certification System (G-SEED). For this purpose, greenbuilding certification systems and supporting assessment systems were analyzed in order to graspthe current trend of the GHG emission assessment on building materials. Roh et al. [6] developedand evaluated the applicability of an optimum design program for the CO2 life cycle assessment(LCA) of a building that can be readily utilized during the planning and design phases. For thispurpose, a database containing information about the CO2-reducing performance and the cost ofenvironmentally-friendly construction technologies that are applicable to apartment houses wasconstructed, and an interpretation program was built based on a simplified technique for assessing thelife cycle CO2 emission of an apartment house and the unit costs based on the inter-industry relationtable. Yang et al. [7] analyzed a reliable procedure to assess the carbon dioxide (CO2) uptake of concreteby carbonation during the service life of a structure and by the recycling of concrete after demolition.To generalize the amount of absorbable CO2 per unit volume of concrete, the molar concentration ofconstituents in hardened cement paste was simplified as a function of the unit content of cement, andthe degree of hydration of the cement paste was formulated as a function of the water-to-cement ratio.Kim et al. [8] evaluated the appropriateness and the reduction performance of the low-carbon-emissionconcrete mix design system and the deduced mix design results using an evolutionary algorithm (EA), theoptimal mix design method, which minimizes the CO2 emission of the concrete mix design. Park et al. [9]proposed a method to assess life cycle CO2 emission using the compressive strength of concrete. Thecompressive strength of concrete used at construction sites was utilized to evaluate CO2 emission.Additionally, comparisons according to the CO2 characteristics of each concrete were also made.

Hasanbeigi et al. [10] analyzed the available information on process description, energy savings,environmental, and other benefits, costs, commercialization status, and references for emergingtechnologies to reduce the cement industry’s energy use and CO2 emission. Ji et al. [11] proposed

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three methods (eco-efficiency, environmental priority strategy (EPS) system, and certified emissionreduction (CER) price) to support the decision-making processes that simultaneously consider costand CO2 emission in acquiring an economical and environment-friendly design.

Yeo et al. [12] proposed an optimization approach developed with a view to allowingdecision-makers to balance sustainability and economic objectives considering an RC frame undergravity and lateral loads. Gartner [13] analyzed the practicality of replacing Ordinary Portland cementswith alternative hydraulic cements that could result in lower CO2 emission per unit volume of concrete.Fraile et al. [14] proposed a methodology for the selection of structural alternatives in residentialbuildings, in which CO2 emission have been used as a measure of environmental impact, according tothe proposal of CEN/TC-350.

Garcia et al. [15] endeavored to determine whether the reduction in producing emissions ofblended cements compensates for the reduced durability and CO2 capture. Miller et al. [16] investigatedthe influence of design age, in addition to mix proportions and geometric aspects, on the GWP(Global Warming Potential) associated with making beams, columns, and a concrete building frame.Lee et al. [17] investigated a sustainable development method such as material, service life, andreusability of concrete in terms of CO2 balance (emission–absorption) and life cycle CO2 of concrete tosuppress the reckless development in pursuit of economic benefits.

Tae et al. [18] evaluated the environmental performance of high-strength concrete used in high-risebuildings as a material of environmental load reduction. Yepes et al. [19] described a methodology tooptimize cost and CO2 emission when designing precast concrete road bridges with a double U-shapecross-section. To this end, a hybrid glowworm swarm optimization algorithm was used to combinethe synergy effect of the local search with simulated annealing and the global search with glowwormswarm optimization.

3. Methodology of CO2 Life Cycle Assessment for Concrete

A system boundary was established for the life cycle CO2 emission evaluation of concrete.The system boundary was selected as the product stage of concrete (cradle to gate) based on ISO14044 [20] and ISO 21930 [21]. The product stage of concrete is divided into the raw material stage,the transportation stage, and the manufacturing stage [22]. The raw material stage refers to CO2

emission during the production of major components of concrete such as cement, aggregate, andwater. The transportation stage’s CO2 emission occurs during the transportation of raw materials tothe ready-mixed concrete manufacturing plant. The manufacturing stage’s CO2 emission comes fromelectricity and oil used in the concrete batch plant. The system boundary for life cycle CO2 emission ofconcrete is shown in Figure 1. Also, Figure 2 is the production process of concrete.

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reduction (CER) price) to support the decision‐making processes that simultaneously consider cost 

and CO2 emission in acquiring an economical and environment‐friendly design. 

Yeo et al. [12] proposed an optimization approach developed with a view to allowing decision‐

makers to balance sustainability and economic objectives considering an RC frame under gravity and 

lateral  loads. Gartner  [13] analyzed  the practicality of  replacing Ordinary Portland  cements with 

alternative hydraulic cements that could result in lower CO2 emission per unit volume of concrete. 

Fraile  et al.  [14] proposed a methodology  for  the selection of structural alternatives  in  residential 

buildings, in which CO2 emission have been used as a measure of environmental impact, according 

to the proposal of CEN/TC‐350. 

Garcia  et  al.  [15]  endeavored  to determine whether  the  reduction  in producing  emissions of 

blended  cements  compensates  for  the  reduced  durability  and  CO2  capture.  Miller  et  al.  [16] 

investigated the influence of design age, in addition to mix proportions and geometric aspects, on the 

GWP (Global Warming Potential) associated with making beams, columns, and a concrete building 

frame. Lee et al. [17] investigated a sustainable development method such as material, service life, 

and  reusability  of  concrete  in  terms  of CO2  balance  (emission–absorption)  and  life  cycle CO2  of 

concrete to suppress the reckless development in pursuit of economic benefits.   

Tae et al. [18] evaluated the environmental performance of high‐strength concrete used in high‐

rise  buildings  as  a  material  of  environmental  load  reduction.  Yepes  et  al.  [19]  described  a 

methodology to optimize cost and CO2 emission when designing precast concrete road bridges with 

a double U‐shape cross‐section. To this end, a hybrid glowworm swarm optimization algorithm was 

used to combine the synergy effect of the local search with simulated annealing and the global search 

with glowworm swarm optimization. 

3. Methodology of CO2 Life Cycle Assessment for Concrete   

A system boundary was established for the life cycle CO2 emission evaluation of concrete. The 

system boundary was selected as the product stage of concrete (cradle to gate) based on ISO 14044 

[20] and  ISO 21930  [21]. The product stage of concrete  is divided  into  the raw material stage,  the 

transportation stage, and the manufacturing stage [22]. The raw material stage refers to CO2 emission 

during  the production of major components of concrete such as cement, aggregate, and water. The 

transportation stage’s CO2 emission occurs during the transportation of raw materials to  the ready‐

mixed concrete manufacturing plant. The manufacturing stage’s CO2 emission comes from electricity 

and oil used in the concrete batch plant. The system boundary for life cycle CO2 emission of concrete 

is shown in Figure 1. Also, Figure 2 is the production process of concrete. 

 

Figure 1. System boundary of the life cycle assessment (LCA) for concrete. Figure 1. System boundary of the life cycle assessment (LCA) for concrete.

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Figure 2. The production process of concrete according to LCA. 

3.1. Raw Material   

CO2  emission  from  concrete  production was  calculated  as  the  sum  of  the  quantity  of  each 

ingredient used for producing 1 m3 of concrete and the CO2 emission factor. The CO2 emission factor 

for cement, aggregate, and water were based on the Korea LCI DB (Life Cycle Inventory DataBase). 

In addition, blast‐furnace slag,  fly ash, and chemical admixtures, which are not database units  in 

Korea, were applied  to  the overseas LCI DB  [23,24]. Equation  (1)  is used  for calculating  the CO2 

emission during  the production of  the raw material required  for manufacturing 1 m3 of concrete. 

Table 1 lists the CO2 emission reference of each ingredient. 

CO2M = ∑(M(i) × CO2 emission factor M) 

(i = 1: cement, 2: aggregate, 3: admixture, 4: water) (1) 

CO2M is the CO2 emission quantity at the raw material stage for the production of a unit of concrete 

[kg‐CO2/m3], M(i) is the amount of material used [kg/m3] of concrete, and CO2 emission factor M is 

the CO2 emission factor [kg‐CO2/kg] for each material.   

Table 1. LCI DB of raw materials. 

Material  Unit  Reference Basis 

Ordinary Portland Cement  kg  National LCI DB (South Korea) 

Coarse aggregate  kg  National LCI DB (South Korea) 

Fine aggregate  kg  National LCI DB (South Korea) 

Blast‐furnace slag powder  kg  Overseas LCI DB (ecoinvent) 

Fly ash  kg  Overseas LCI DB (ecoinvent) 

Water  kg  National LCI DB (South Korea) 

Chemical Admixture compound  kg  Overseas LCI DB (ecoinvent) 

 

Figure 2. The production process of concrete according to LCA.

3.1. Raw Material

CO2 emission from concrete production was calculated as the sum of the quantity of eachingredient used for producing 1 m3 of concrete and the CO2 emission factor. The CO2 emission factorfor cement, aggregate, and water were based on the Korea LCI DB (Life Cycle Inventory DataBase).In addition, blast-furnace slag, fly ash, and chemical admixtures, which are not database units in Korea,were applied to the overseas LCI DB [23,24]. Equation (1) is used for calculating the CO2 emissionduring the production of the raw material required for manufacturing 1 m3 of concrete. Table 1 liststhe CO2 emission reference of each ingredient.

CO2M “ř

pMpiqˆCO2 emission factor Mqpi “ 1 : cement, 2 : aggregate, 3 : admixture, 4 : waterq

(1)

CO2M is the CO2 emission quantity at the raw material stage for the production of a unit of concrete[kg-CO2/m3], M(i) is the amount of material used [kg/m3] of concrete, and CO2 emission factor M isthe CO2 emission factor [kg-CO2/kg] for each material.

Table 1. LCI DB of raw materials.

Material Unit Reference Basis

Ordinary Portland Cement kg National LCI DB (South Korea)Coarse aggregate kg National LCI DB (South Korea)

Fine aggregate kg National LCI DB (South Korea)Blast-furnace slag powder kg Overseas LCI DB (ecoinvent)

Fly ash kg Overseas LCI DB (ecoinvent)Water kg National LCI DB (South Korea)

Chemical Admixture compound kg Overseas LCI DB (ecoinvent)

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3.2. Transportation

For assessing the CO2 emission due to transportation, the total quantity used and the loadfor each component were measured to calculate the number of vehicles required for transportation.The calculated number of vehicles, the distance, and the fuel efficiency of each vehicle were usedfor assessing the CO2 emission. In this study, the truck’s speed and traffic were not considered.Equation (2) is used for calculating the CO2 emission during the transportation process. Table 2 liststhe CO2 emission reference of each transportation method.

CO2T “ř

rpMpiq{Ltqˆ pd{eqˆCO2 emission factor Tspi “ 1 : cement, 2 : coarse aggregate, 3 : fine aggregate, 4 : admixtureq

(2)

Here, CO2T is the quantity of CO2 emitted during the transportation of a unit of produced concrete[kg-CO2/m3], M(i) is the amount of material used [kg/m3] in the concrete, Lt is the transportationload [tons], d is the transportation distance [km], e is the fuel efficiency [km/L], and CO2 emissionfactor T is the CO2 emission factor [kg-CO2/kg] of the energy resource.

Table 2. LCI DB of transportation method.

Transportation Equipment Unit Reference Basis

Truck km National LCI DB (South Korea)Train km National LCI DB (South Korea)

3.3. Manufacturing

The CO2 emitted from concrete manufacturing can be calculated using the amount of energyconsumed by the manufacturing equipment for producing 1 m3 of concrete and converting that to CO2.For this approach, the concrete manufacturing process must be divided, and the consumed energymust be calculated. The concrete manufacturing process can be divided into the following five stages:loading, storage, transportation, measurement for mixing, and mixing. The equipment required, thedata related to the power, and the fossil fuel energy consumed in each stage are examined; then, byanalyzing the ratio between the capacity of each piece of equipment and the total amount of electricityused, the energy consumed for manufacturing 1 m3 of concrete can be calculated. Equation (3) is usedfor calculating the CO2 emission during the manufacturing process, and Table 3 lists the CO2 emissionreference of energy source.

CO2F “ř

rpEpiq{RqˆCO2 emission factor Fspi “ 1 : electricity usage, 2 : oil usage, 3 : water usageq

(3)

Here, CO2F is the amount of CO2 emitted during the concrete manufacturing stage for producinga unit of concrete [kg-CO2/m3], R denotes the annual RMC production [m3/year], E(i) denotes theannual energy usage [unit/year], and CO2 emission factor F is the CO2 emission factor [kg-CO2/kg]of an energy resource.

Table 3. LCI DB of energy source.

Category Unit Reference Basis

Crude Oil ` National LCI DB (South Korea)Diesel ` National LCI DB (South Korea)

Kerosene ` National LCI DB (South Korea)LPG m3 National LCI DB (South Korea)

Electricity kwh National LCI DB (South Korea)

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4. Analysis of CO2 Emission for Concrete

The analyzed buildings were constructed in South Korea. These include three office buildings,four multipurpose buildings, and three apartment buildings; three of 10 buildings are located inSeoul, one in Busan, and 6 in Incheon. The characteristics of each project are summarized in Table 4.Moreover, the CO2 emission of concrete using construction projects was evaluated by the methodologyof CO2 life cycle assessment for concrete.

Assessment results were analyzed separately by the material type, the building type, and thelocal characteristics [25–27].

Table 4. Project characteristics.

Category Use Regional Category # of Floors Gross Area (m2)

1 O-S-12Office

Seoul 12 219,2612 O-S-19 Seoul 19 22,9973 O-I-45 Incheon 45 201,571

4 C-S-66

Commercial

Seoul 66 462,0005 C-B-58 Busan 58 433,8126 C-I-47 Incheon 47 204,5537 C-I-49 Incheon 49 184,836

8 A-I-32Apartment

Incheon 32 190,5989 A-I-38 Incheon 38 121,225

10 A-I-27 Incheon 27 284,044

O: Office, C: Commercial, A: Apartment, S: Seoul, I: Incheon, B: Busan.

4.1. Material Characteristics

Material characteristics can be interpreted based on multiple variables such as strength, slumpand flow, project, building usage, region, etc. The slump and flow of concrete did not have a largeinfluence on CO2 emission for the same compressive strength. This is because, generally, for the sameslump and flow, water-reducing admixture and other similar materials are used for controlling slumpand flow rather than material mixture. Therefore, a comparison of the same compressive strengthconcrete for multiple projects as a variable does not consider the “mixture per project” variable. In caseswhere the installation parts are different and strengths are the same, such as concrete for structure partinstallation or concrete for basis installation, the differences of slump and flow for the concrete may becompared. However, generally, in such cases, this is the reason for the difference in strength ratherthan differences in slump and flow for the case of using different installation parts when selectingconcrete strength at a construction site [28].

The analysis of CO2 emission was divided into the structure part and basis part. This is becausemuch of the cement is substituted with blast-furnace slag for reducing heat generation during hydrationto ensure that the CO2 emission is very low. The compressive strength of concrete using the projectscan be divided into 16 levels ranging from 18 MPa to 65 MPa, and further in terms of slump and flow;thus, in total, 41 comparison factor data can be obtained. According to Figure 3, with regard to theconcrete used for structure as well as the basis, the CO2 emission tends to increase with the strength;however, the increase in the latter case is 10% lower than that in the former case. This is because theconcrete used for the basis contains a relatively lower amount of cement for hydration heat reduction,and admixture such as blast-furnace slag is added. As for the basis part, 60-MPa concrete results in1.5-times higher CO2 emission than 24-MPa concrete. As for the structures part, both blast-furnaceslag and cement showed the same rate at 10%; in the case of the basis, the cement was substituted withground granulated blast-furnace slag (GGBS). The reason for using a large quantity of blast-furnaceslag is because the corporate policy of the assessment target construction company involves the usageof blast-furnace slag, and this usage was executed under a thorough concrete quality management andmix management scheme.

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In the case of the O-S-12 and O-S-19 projects, both using concrete of 18-Mpa strength, the totalamount of material for 1 m3 of RMC were almost similar at 2311 kg and 2323 kg, respectively, butthere was a difference of about 38 kg-CO/m3 in their respective CO2 emission levels, which stoodat 252 kg-CO/m3 and 214.80 kg-CO/m3, respectively. This is because the amounts of cement usedfor these projects were 227 kg/m3 and 182 kg/m3, respectively, with blast-furnace slag and fly ashaccounting for the difference. In the case of the same strength, the total mixed quantities of cement,aggregate, blast-furnace slag, and fly ash were similar, but the amount of cement used caused thedifference in CO2 emission. Furthermore, RMC of the 25-30-500 standard was used in the following5 projects as shown in Figure 4: C-S-66, C-B-58, C-I-47, C-I-49, and A-I-32. Even for the same strengthand slump, there were differences based on the installation part as in the cases of C-S-66 and C-B-58.Furthermore, and for cases such as C-S-66 and C-I-47, which were of the same type and had the sameinstallation location, local differences led to the proposal of a mix design with increased use of flyash for increasing resistance to salt attack, as is suited to coastal regions. In the case of the C-B-58project, the material-stage emission was low because all cement was substituted with blast-furnace slagcement and blast-furnace fine particles, as can be inferred from Table 5, which compares the variousmultipurpose projects considered. This is because the C-B-58 project mixed through technologicalreview to reduce hydration heat and save costs during the installation of basic mat concrete.

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252 kg‐CO/m3 and 214.80 kg‐CO/m3, respectively. This is because the amounts of cement used for 

these  projects were  227  kg/m3  and  182  kg/m3,  respectively, with  blast‐furnace  slag  and  fly  ash 

accounting for the difference. In the case of the same strength, the total mixed quantities of cement, 

aggregate, blast‐furnace slag, and fly ash were similar, but the amount of cement used caused the 

difference in CO2 emission. Furthermore, RMC of the 25‐30‐500 standard was used in the following 

5 projects as shown in Figure 4: C‐S‐66, C‐B‐58, C‐I‐47, C‐I‐49, and A‐I‐32. Even for the same strength 

and slump, there were differences based on the installation part as in the cases of C‐S‐66 and C‐B‐58. 

Furthermore, and for cases such as C‐S‐66 and C‐I‐47, which were of the same type and had the same 

installation location, local differences led to the proposal of a mix design with increased use of fly ash 

for increasing resistance to salt attack, as is suited to coastal regions. In the case of the C‐B‐58 project, 

the material‐stage  emission was  low  because  all  cement was  substituted with  blast‐furnace  slag 

cement and blast‐furnace fine particles, as can be inferred from Table 5, which compares the various 

multipurpose projects considered. This  is because  the C‐B‐58 project mixed  through  technological 

review to reduce hydration heat and save costs during the installation of basic mat concrete. 

 

Figure 3. CO2 emission according to concrete strength. 

 

Figure 4. Comparison of CO2 emission per project (30 MPa‐500mm slump example). 

 

Figure 3. CO2 emission according to concrete strength.

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252 kg‐CO/m3 and 214.80 kg‐CO/m3, respectively. This is because the amounts of cement used for 

these  projects were  227  kg/m3  and  182  kg/m3,  respectively, with  blast‐furnace  slag  and  fly  ash 

accounting for the difference. In the case of the same strength, the total mixed quantities of cement, 

aggregate, blast‐furnace slag, and fly ash were similar, but the amount of cement used caused the 

difference in CO2 emission. Furthermore, RMC of the 25‐30‐500 standard was used in the following 

5 projects as shown in Figure 4: C‐S‐66, C‐B‐58, C‐I‐47, C‐I‐49, and A‐I‐32. Even for the same strength 

and slump, there were differences based on the installation part as in the cases of C‐S‐66 and C‐B‐58. 

Furthermore, and for cases such as C‐S‐66 and C‐I‐47, which were of the same type and had the same 

installation location, local differences led to the proposal of a mix design with increased use of fly ash 

for increasing resistance to salt attack, as is suited to coastal regions. In the case of the C‐B‐58 project, 

the material‐stage  emission was  low  because  all  cement was  substituted with  blast‐furnace  slag 

cement and blast‐furnace fine particles, as can be inferred from Table 5, which compares the various 

multipurpose projects considered. This  is because  the C‐B‐58 project mixed  through  technological 

review to reduce hydration heat and save costs during the installation of basic mat concrete. 

 

Figure 3. CO2 emission according to concrete strength. 

 

Figure 4. Comparison of CO2 emission per project (30 MPa‐500mm slump example). 

 

Figure 4. Comparison of CO2 emission per project (30 MPa-500 mm slump example).

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Table 5. CO2 emission comparison of C-B-58, C-I-49 project.

CategoryC-B-58 (30 MPa-500 mm slump) C-I-49 (30 MPa-500 mm slump)

Mix Design (kg/m3) CO2 Emission Mix Design (kg/m3) CO2 Emission

Ordinary Cement Not included Not included 211 196.44Water 160 1.12 160 1.12Coarse aggregate 929 3.71 953 3.81Fine aggregate 831 2.49 806 2.42Blast-furnace slag powder 308 62.83 211 43.04Admixture 4.92 1.23 4.01 1.00Flyash 102 63.21 Not included Not included

4.2. Building Type Characteristics

The characteristics of each building type are shown in Figure 5. For apartment buildings andoffices, the CO2 emission levels were similar, and multipurpose buildings had the lowest emissionsoverall. The increase in concrete strength led to an increase in CO2 emission, but the multipurposebuildings using high-strength concrete emitted lower CO2 than the other building types. This is becauseoffices and apartment buildings used a higher amount of cement for high-strength concrete, whereasmultipurpose buildings used an increased amount of blast-furnace ash or fly ash. For multipurposebuildings, the concrete installation cycle is very important, owing to their sizes and characteristics.Thus, multipurpose buildings warrant a considerable daily installation effort, which involves mixingagainst hydration heat, leading to different CO2 emission levels. The reason that offices have less CO2

emission than apartments is the decrease in concrete volume (m3) by applying high-strength concreteto office design [29,30].

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Table 5. CO2 emission comparison of C‐B‐58, C‐I‐49 project. 

Category 

C‐B‐58 (30 MPa‐500mm slump)  C‐I‐49 (30 MPa‐500mm slump) 

Mix Design 

(kg/m3) CO2 Emission 

Mix Design 

(kg/m3) CO2 Emission 

Ordinary Cement  Not included  Not included  211  196.44 

Water  160  1.12  160  1.12 

Coarse aggregate  929  3.71  953  3.81 

Fine aggregate  831  2.49  806  2.42 

Blast‐furnace slag powder  308  62.83  211  43.04 

Admixture  4.92  1.23  4.01  1.00 

Flyash  102  63.21  Not included  Not included 

4.2. Building Type Characteristics 

The characteristics of each building type are shown in Figure 5. For apartment buildings and 

offices, the CO2 emission levels were similar, and multipurpose buildings had the lowest emissions 

overall. The increase in concrete strength led to an increase in CO2 emission, but the multipurpose 

buildings using high‐strength  concrete  emitted  lower CO2  than  the other building  types. This  is 

because offices and apartment buildings used a higher amount of cement for high‐strength concrete, 

whereas multipurpose  buildings  used  an  increased  amount  of  blast‐furnace  ash  or  fly  ash.  For 

multipurpose buildings, the concrete  installation cycle  is very  important, owing to their sizes and 

characteristics. Thus, multipurpose buildings warrant a considerable daily installation effort, which 

involves mixing against hydration heat,  leading  to different CO2 emission  levels. The  reason  that 

offices have less CO2 emission than apartments is the decrease in concrete volume (m3) by applying 

high‐strength concrete to office design [29,30]. 

 

Figure 5. Comparison of CO2 emission according to building type. 

4.3. Local Characteristics 

As shown in Figure 6, Seoul was found to have higher CO2 emission compared to Incheon and 

Busan; Busan has just one case of an ultra‐high‐rise multipurpose building using high‐liquidity RMC, 

so it should be excluded. In the comparison of Seoul and Incheon, it can be seen that the CO2 emission 

of the former are higher than the latter by about 27 (kg‐CO2/m3). This is partly because Incheon has a 

greater distribution of multipurpose buildings with low CO2 emission than Seoul does; furthermore, 

a greater amount of blast‐furnace slag was used in Incheon for increasing the structure resistance to 

salt attack, since Incheon is a coastal city. 

Figure 5. Comparison of CO2 emission according to building type.

4.3. Local Characteristics

As shown in Figure 6, Seoul was found to have higher CO2 emission compared to Incheon andBusan; Busan has just one case of an ultra-high-rise multipurpose building using high-liquidity RMC,so it should be excluded. In the comparison of Seoul and Incheon, it can be seen that the CO2 emissionof the former are higher than the latter by about 27 (kg-CO2/m3). This is partly because Incheon has agreater distribution of multipurpose buildings with low CO2 emission than Seoul does; furthermore, agreater amount of blast-furnace slag was used in Incheon for increasing the structure resistance to saltattack, since Incheon is a coastal city.

When analyzed for multipurpose buildings in each area, the Incheon-area ones have loweremissions than those in the other areas; this can be attributed to the salt-attack-resistant mix used in

Sustainability 2016, 8, 348 9 of 14

the region. As for the difference in CO2 emission during the transportation stage among the threeareas, the RMC company of the Incheon area mostly used local materials for aggregate, admixture,and compound except cement; similarly, the Seoul-area projects used aggregate from Seoul butadmixture/compound from Incheon, thus resulting in lower CO2 emission than the Busan-areaprojects [31,32].

Sustainability 2016, 8, 348  9 of 14 

When  analyzed  for multipurpose  buildings  in  each  area,  the  Incheon‐area  ones  have  lower 

emissions than those in the other areas; this can be attributed to the salt‐attack‐resistant mix used in 

the region. As for the difference in CO2 emission during the transportation stage among the three 

areas, the RMC company of the Incheon area mostly used local materials for aggregate, admixture, 

and  compound  except  cement;  similarly,  the  Seoul‐area  projects  used  aggregate  from  Seoul  but 

admixture/compound  from  Incheon,  thus  resulting  in  lower  CO2  emission  than  the  Busan‐area 

projects [31,32]. 

 

Figure 6. Comparison of CO2 emission according to local characteristics. 

5. Impact Analysis of the CO2 Emission on Construction Planning 

The  CO2  reduction  plan  according  to  the  analysis  of  these  10  projects was  applied  to  the 

construction site. This site is an RC structure office building with a gross area of 219,000 m2 located 

in South Korea.   

It contains four buildings with 5 underground floors and 12 aboveground floors as shown Table 6.   

Table 6. Target project for case study.   

Project Overview 

Area  Bundang‐gu, Gyoenggi‐do in South Korea 

Purpose  Office, commercial 

Builder  P Company in South Korea 

Gross  219,000 m2 

Building  16,270 m2 

Land  28,192 m2 

Period  2009.06–2012.02 

Size  5 underground floors, 12 ground floors 

The work done on site included a proposed plan for the pillar design change of the above project, 

where the original design strength was 30 MPa at 1532 m3, and an SRC structure, as summarized in 

Table 7. The steel frame was deleted from the structure, and the structure itself was changed to the 

RC‐type using high‐strength concrete, for which the quantity of each material was compared for ALT 

1 and 2. In the case of ALT 1, the pillar size was maintained at 800 mm × 800 mm, but high‐strength 

concrete was used, and steel rebar was increased in addition to the removal of the steel frame. In the 

case of ALT 2, dimensions of the underground pillar were changed to 1100 mm × 800 mm, and the 

ground floor was maintained at 800 mm × 800 mm, but high‐strength concrete was used for reducing 

the amount of concrete required.  In  this assessment,  the method described above was applied, as 

summarized in Table 8. Here, CO2 emission per m3 of each RMC used an average value for 30 MPa, 

Figure 6. Comparison of CO2 emission according to local characteristics.

5. Impact Analysis of the CO2 Emission on Construction Planning

The CO2 reduction plan according to the analysis of these 10 projects was applied to theconstruction site. This site is an RC structure office building with a gross area of 219,000 m2 located inSouth Korea.

It contains four buildings with 5 underground floors and 12 aboveground floors as shown Table 6.

Table 6. Target project for case study.

Project Overview

Area Bundang-gu, Gyoenggi-do in South KoreaPurpose Office, commercialBuilder P Company in South KoreaGross 219,000 m2

Building 16,270 m2

Land 28,192 m2

Period 2009.06–2012.02Size 5 underground floors, 12 ground floors

The work done on site included a proposed plan for the pillar design change of the above project,where the original design strength was 30 MPa at 1532 m3, and an SRC structure, as summarized inTable 7. The steel frame was deleted from the structure, and the structure itself was changed to theRC-type using high-strength concrete, for which the quantity of each material was compared for ALT 1and 2. In the case of ALT 1, the pillar size was maintained at 800 mm ˆ 800 mm, but high-strengthconcrete was used, and steel rebar was increased in addition to the removal of the steel frame. In thecase of ALT 2, dimensions of the underground pillar were changed to 1100 mm ˆ 800 mm, and theground floor was maintained at 800 mm ˆ 800 mm, but high-strength concrete was used for reducingthe amount of concrete required. In this assessment, the method described above was applied, assummarized in Table 8. Here, CO2 emission per m3 of each RMC used an average value for 30 MPa,while the mixtures of strengths 45 MPa and 50 MPa used much admixture, such as blast-furnace slag.Thus far, the mix design of this project shows that more cement has been used than the blast-furnace

Sustainability 2016, 8, 348 10 of 14

slag, but as the framework progresses, the proportion of blast-furnace slag used will increase.The basic unit CO2 emission of steel rebar and steel frame was assessed using data obtained throughinter-industry analysis. The above items were analyzed for the application of eco-friendly constructionmethods and V.E. to the target project, and it is expected to be applicable across all processes if furtherstudies based on this study are executed and methods for reducing CO2 emission are developed.Table 7 lists the quantities of increase/decrease of RMC, steel rebar, and steel frame in the revised plancompared to those in the original, and Table 9 lists the CO2 emission deduced by applying the CO2

basic unit per material to this quantity [33,34].

Table 7. Material fluctuation according to pillar strength change.

Category Original Plan ALT 1 ALT 2

Concrete (m3)1532 525 - 30 MPa

- 1007 1007 45 MPa- - 430 50 MPa

Rebar (ton)199 - SD40

- 589 618 SD50

Steel-frame 747 - - SM49

Table 8. Reduction technology of CO2 emission for concrete.

Category Detail Content Note

MaterialCharacteristics

Increased use of blast-furnace slag for hydration heat reduction not applied

Increased use of blast-furnace slag and fly ash in case of usingthe same strength applied

Reduced quantity by applying high-strength concrete applied

Assessment method for material procurement location distancewhen selecting RMC company not applied

Building typeCharacteristics

Use of mix with low CO2 emission for ultra-high-rise even incase of buildings using low-strength applied

Local Characteristics Mix design according to local characteristics applied

Table 9. CO2 emission difference according to pillar change [Unit: kg-CO2].

Category Original Plan ALT 1 ALT 2

Concrete

30 MPa 519,930 178,174 -

45 MPa - 299,985 299,985

50 MPa - 132,788

80 MPa - - -

RebarSD40 877 - -

SD50 - 2597 2725

Steel-frame SM49 3869 - -

Total 524,676 480,756 435,495

Reduction ratio (%) - 15% 23%

As shown in Figure 7, the RC structure showed less CO2 emission than the SRC structure, andhigh-strength concrete showed less CO2 emission than the low-strength concrete. The CO2 emission ofALT 2 was 85% that of the original. Even for low-rise offices, the application of high-strength concretecan reduce the required concrete quantity as well as CO2 emission. In the case of pillars, the use of

Sustainability 2016, 8, 348 11 of 14

high-strength CO2 emission must result in increased slab concrete strength, and, accordingly focusedmanagement for concrete installation is necessary. Here, several CO2 emission reduction methods maybe proposed. The first step is the application of high-strength concrete. As can be inferred from the mixdesign comparison according to pillar strength change, CO2 emission was reduced with the applicationof high-strength concrete. In the case of high-strength, the required quantities of concrete and steelrebar are reduced. This decrease led to the reduction of CO2 emission. The second step is the mixture.It was found that CO2 emission levels were different, even for the same strength and slump. When theconstruction company prepares a standard mix design for RMC, the use of blast-furnace slag canreduce the amount of cement, thus leading to decreased CO2 emission. Especially for basic concrete,the substitution rate can be increased for saving a large amount of CO2. If the mix design that can saveraw cost by using high-strength concrete and blast-furnace slag in multipurpose buildings and similarstructures is managed across the enterprise, high-strength concrete could be used in low-rise buildingswithout any additional cost. Finally, if the weight of RMC company selection is increased throughanalysis, considering the distance between the RMC company and the site, the material procurementsource, and the production equipment during the selection of an RMC company, CO2 emission couldbe reduced [35,36].

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Building type 

Characteristics 

Use of mix with low CO2 emission for ultra‐high‐rise even in case of 

buildings using low‐strength applied 

Local 

Characteristics Mix design according to local characteristics  applied 

Table 9. CO2 emission difference according to pillar change [Unit: kg‐CO2]. 

Category  Original Plan  ALT 1  ALT 2 

Concrete 

30 MPa  519,930  178,174  ‐ 

45 MPa  ‐  299,985  299,985 

50 MPa  ‐    132,788 

80 MPa  ‐  ‐  ‐ 

Rebar SD40  877  ‐  ‐ 

SD50  ‐  2597  2725 

Steel‐frame  SM49  3869  ‐  ‐ 

Total  524,676  480,756  435,495 

Reduction ratio (%)  ‐  15%  23% 

 

Figure 7. Comparison of CO2 emission according to pillar change. 

6. Discussion and Limitations 

This study aimed to assess and analyze the CO2 emission of concrete, which is used according 

to building type and region. 

Then,  it  proposed  a  method  to  reduce  CO2  emission  in  the  use  of  concrete  in  building 

construction. In addition, CO2 emission was assessed by applying the proposed technology to the 

target building. 

However, this study has the following limitations:   

First, this study examined concrete only among diverse construction materials. Therefore, it is 

limited in assessing the CO2 emission of buildings. Among the construction materials used during a 

construction stage,  the  following seven materials accounted for 95% of  total CO2 emission: ready‐

mixed  concrete,  reinforced  rod,  steel  frame,  paint,  glass,  concrete mix,  and  insulating material. 

Therefore, there should be further studies on the construction materials with high CO2 emission to 

assess the CO2 emission of buildings and propose their reduction technology. 

Second, this study did not cover the CO2 absorptions by concrete carbonation. Concrete loses 

alkalinity after CO2 in the air is absorbed into concrete and generates chemical reactions. Concrete is 

not directly degraded by carbonation. If the carbonation of a reinforced concrete structure reaches up 

to  the  surface  of  a  reinforcing  rod  beyond  the  cover  thickness,  the  passivity  layer  around  the 

reinforcing rod is destructed, initiating corrosion. From the perspective of ecological environment, 

Figure 7. Comparison of CO2 emission according to pillar change.

6. Discussion and Limitations

This study aimed to assess and analyze the CO2 emission of concrete, which is used according tobuilding type and region.

Then, it proposed a method to reduce CO2 emission in the use of concrete in building construction.In addition, CO2 emission was assessed by applying the proposed technology to the target building.

However, this study has the following limitations:First, this study examined concrete only among diverse construction materials. Therefore, it is

limited in assessing the CO2 emission of buildings. Among the construction materials used during aconstruction stage, the following seven materials accounted for 95% of total CO2 emission: ready-mixedconcrete, reinforced rod, steel frame, paint, glass, concrete mix, and insulating material. Therefore,there should be further studies on the construction materials with high CO2 emission to assess theCO2 emission of buildings and propose their reduction technology.

Second, this study did not cover the CO2 absorptions by concrete carbonation. Concrete losesalkalinity after CO2 in the air is absorbed into concrete and generates chemical reactions. Concrete isnot directly degraded by carbonation. If the carbonation of a reinforced concrete structure reaches upto the surface of a reinforcing rod beyond the cover thickness, the passivity layer around the reinforcingrod is destructed, initiating corrosion. From the perspective of ecological environment, concrete’sabsorption of CO2 in the air is beneficial. However, durability should be considered. In other words,

Sustainability 2016, 8, 348 12 of 14

the absorption of CO2 absorptions during the construction and use of reinforced concrete structuresshould be assessed.

However, this study analyzed a construction stage (required) only in the LCA, without consideringthe use, maintenance, and destruction/disposal stages.

Third, a reliability test on the proposed CO2 emission reduction technology is not enoughbecause only one case was analyzed. Therefore, there should be further verifications through diversecase studies.

7. Conclusions and Future Work

Using the proposed concrete CO2 emission assessment method, the characteristics of constructionprojects in terms of area and purpose were analyzed for the causes of differences in CO2 emission basedon concrete strength, structure type, and structure area. This was accomplished by assessing eachstage of construction, i.e., material procurement, transportation, and manufacturing. In the analysisaccording to building types, CO2 emission was found to decrease, from highest to lowest, apartmentbuildings, office buildings, and multipurpose buildings. This can be attributed to the increaseduse of blast-furnace slag and fly ash as a cement-replacement compound material in multipurposebuildings rather than using concrete of the same strength, as in the case of apartment buildings andoffices. Under-construction projects were selected for the application/assessment of the developedCO2 emission reduction method. As a result, the RC-structure, high-strength concrete applicationshowed a reduction of about 17% in CO2 emission compared to the SRC-structure, low-strengthconcrete. In RC-structure pillars, high-strength pillars were found to result in about a 10% reduction inCO2 emission than low-strength concrete pillars.

The CO2 emission reduction method at the construction stage can be summarized as theapplication of high-strength concrete, the standardization of reduction mix design using blast-furnaceslag, and the selection of RMC companies with low CO2 emission.

The CO2, NOx, and SO2 emitted in concrete production affect the acidification and eutrophicationas well as global warming. NOx and SO2 come down on the ground in such forms as acid rain andacid snow and are absorbed in lakes, rivers, and soil. The acidification and eutrophication caused byNOx and SO2 is a major cause of red tide and reinforced concrete structure degradation.

In the future, the LCA method and program (software) for various environmental load is neededand will be the topic of the next paper by the present researchers.

Acknowledgments: This research was supported by a grant (Code 11-Technology Innovation-F04) fromConstruction Technology Research Program (CTIP) funded by the Ministry of Land, Infrastructure and Transport.

Author Contributions: The paper was written and revised developed by Tae Hyoung Kim. Chang U Chaeconducted the experimental and analytical works. Gil Hwan Kim and Hyoung Jae Jang designed and supervisedthe project. All authors contributed to the analysis and conclusion, and revised the paper. All authors read andapproved the final manuscript

Conflicts of Interest: The authors declare no conflict of interest.

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